102 A STUDY OF THE ABSORPTION SPECTRA. 



are shown that are not exhibited in other spectrograms. It will thus be 

 seen that the a, b, c, d, j, and k bands of the solution agree fairly well with 

 those of the crystal, and that the crystal bands /, g, h, and i are shifted 

 towards the red with reference to the bands in the aqueous solution. 



Effect of Dilution on the Uranyl Bands. 



The effect of dilution on the position and intensity of the blue-violet, 

 the ultra-violet, and the uranyl bands of the acetate, nitrate, and sulphate 

 of uranyl in water was tried. The absorption spectra of solutions about 

 1 normal and 3 mm. deep were photographed along by the side of the absorp- 

 tion spectra of 0.008 normal solutions of the same salts 380 mm. deep. 

 The absorption consisted of the blue-violet band, the ultra-violet band, and 

 the a, b, c, i, j, and k bands. Between the blue-violet and ultra-violet 

 bands there was the transmission band containing i, j, and k. For each 

 of the three salts this transmission band was much weaker for the dilute 

 solution, whereas in the cases of the sulphate and nitrate the long wave- 

 length transmission edge of the blue-violet band was stronger for the more 

 dilute solution. The opposite was true of the acetate solution. In the 

 dilute solution of the acetate the band? were more intense than for the 

 more concentrated solution. There was no noticeable change in the posi- 

 tion of the bands. Neither the intensity nor the position of the uranyl 

 nitrate or the uranyl sulphate bands was changed by the above dilution. 



Plate 65, A, represents the spectrogram comparing the spectra of the 

 same amount of uranyl salt in a concentrated and in a dilute solution. 

 Starting w r ith the strip adjacent to the numbered scale we have the absorp- 

 tion spectra of a 1.1 normal solution of uranyl nitrate in water, the depth 

 of the cell being 3 mm. The next spectrogram is of the same solution. 

 Then distilled water was poured into the solution until the length of column 

 was 380 mm. The absorption spectrum of this solution is given in the 

 third strip. The fourth strip represents the absorption of a 0.75 normal 

 solution of uranyl sulphate, the depth of cell being 4 mm. The fifth strip 

 is for the same solution diluted until the depth was 380 mm. The sixth 

 strip represents the absorption of a 0.188 normal solution of uranyl acetate 

 14 mm. deep. The last strip is for the same solution diluted to a depth of 

 380 mm. 



A more detailed study was made as to whether Beer's law holds for 

 uranyl nitrate and for the other uranyl salts. The method of taking the 

 spectrograms is the same as that used for the potassium salts. 



Beer's law was found to hold for dilute solutions of uranyl nitrate in 

 water. When the concentration is greater than 0.5 normal the absorption 

 is greater than it should be if Beer's law held. 



Uranyl Nitrate in Nitric Acid. 



Ordinary uranyl nitrate (U0 2 (N0 3 ) 2 6H 2 0) was dissolved in very strong 

 nitric acid. A spectrogram (Plate 70, B) was made of this solution, differ- 

 ent depths of cell being used. 



The presence of strong nitric acid has a very great effect upon the 

 absorption spectra of uranyl nitrate. In general, it causes the band 



